Finally, we get to DNA sequencing uses: if we can identify certain sequences of DNA, like finding common sequences for hair, for bones, for each eye, for parts of the brain... we then have a map of what that DNA is supposed to build into. We should be able to have a piece of DNA from a person, without ever seeing that person exist, like taking a DNA sample from a foetus... and tell how tall that person will grow, what their skeleton and facial features will be shaped like, what color their skin will be, how strong they will be naturally; if we have a piece of DNA that was left somewhere (like a crime scene), then that DNA can be compared with DNA from a known crime suspect, and if their unique DNA sequences match, we know it's the same person.
Further, in the field of crime for example, if we take a piece of DNA from a crime scene and we don't have a suspect to compare it to... the future hope is that we will know so much about a DNA's sequence that we can actually build a model of that person, complete with accurate facial features and hair color and shape, actually build an accurate likeness of that person, almost 'from scratch' - from DNA. This can also hopefully one day be done for crime victims whose identities are not known.
In short, we are in a race to find a way to map out the complete sequence of a human DNA strand and learn both the general characteristics it contains, and how each of those is also different from the same area of DNA in another person. If we identify the basic genetic sequence, and where along the DNA strand it is, of, say, a leg; then we will be able to compare 'leg' DNA sequences between individuals and see how they differ to make longer or shorter, thicker or thinner, legs. If we compare 'brain' DNA sequences, we should be able to find how changing that sequence will make one person more or less capable of intelligence. Finding the DNA sequence that tells our cells how to age at a certain rate, might be alterable in the far future so we can age more slowly and live longer youths.
DNA sequencing is already being used extensively for the diagnosis of various diseases, and the future promises to give patients precise personalized treatment developed on the basis of that patient's unique DNA sequence.
Below: DNA sequencing is used primarily in genetics laboratories, and also in crime forensics. DNA testing becomes more and more refined, and certain kinds of testing kits are now available in small portable units; perhaps one day a complete DNA sequencing kit will be available in a kit this size... or smaller?
Genetics is perhaps the largest of the DNA sequencing uses; genetics is the study of how DNA replicates and transfers from parent to offspring. Scientists study genetics to determine how DNA sequences change; how a strand of DNA sunders apart, or 'unzips', how new identical strands come together in DNA for one person, and how they come together differently for DNA that is being used to create offspring. Genetics determines how that offspring will look and operate; how your child will look the same as you, how they will look different than you, and how all their parts will be the same as and yet different from yours.
There are countless uses for DNA sequencing, with humans, animals, and plants, and the field of genetics is racing to unlock the secrets of DNA sequencing so they can discover what makes us what we are... and perhaps learn how to alter the building blocks of what we are... hopefully for the better.